The present invention relates to medical multilayer sealant films, and more particularly to a medical multilayer sealant film which is useful as a material for forming the innermost layer of films for medical containers, medical container packaging films and medical container covering films and methods for preparing the same.
From the viewpoint of preventing deterioration of medicinals or breakage of containers and ensuring see-through properties, single-layer films or multi-layered films which are excellent in gas barrier properties, moisture impermeability, heat resistance, impact resistance and transparency have heretofore been used generally as plastic film materials, for example, for making medical containers, packaging medical containers or covering medical containers. These film materials include as a component a base film. Examples of resin material for the base film is, for example, nylon, polyethylene terephthalate, polyvinyl alcohol or the like.
Further in order to give improved heat-sealing properties, it has been practice to laminate a sealant film to the base film of the film material with a silicone, epoxy, urethane, urethane-epoxy, acryl or like adhesive. Chiefly used as the sealant film in this case is a film of resin having a low melting point and low density, such as low-density polyethylene. Such a resin film affords a high heat-sealing strength, permits sealing at a low temperature, gives a specified heat-sealing strength despite adhesion of dust or the like, and is therefore excellent in quality and properties as a sealant film.
With the film material comprising the base film, adhesive layer and sealant film, the base film and the adhesive often contain contaminants.
These contaminants and causes for contamination are as follows.
(1) Various additives added to the material to be formed into the base film for giving improved properties to the film. Such additives are phthalic acid esters [(such as dioctyl phthalate (DOP), di-n-butyl phthalate (DNBP), diethyl phthalate (DEP), diethylhexyl phthalate (DEHP)], chlorinated paraffin, adipic acid esters, fatty acid amide, phosphorus derivatives antioxidants, phenol derivatives antioxidants, etc.
(2) It is likely that the extruder die will be coated with a rust inhibitor or release agent (such as silicone oil). The rust inhibitor or release agent adheres to and contaminates the base film when it is formed.
(3) Contamination due to adhesion of the contaminant or contaminant-containing water to the outer surface of the base film.
(4) In the case where the base film contains nylon resin, adipic acid or caprolactam as a component of the nylon resin.
(5) A reaction product present in the adhesive.
The sealant film providing the innermost layer of the film material conventionally available has no barrier properties to these contaminants, so that if the base film and/or the adhesive contains the contaminant, the contaminant migrates to the inside of the innermost layer through the adhesive layer and the sealant film.
Accordingly, the products prepared from the film material, such as medical containers, medical container packaging bags or medical container covers, are unable to protect the contents, such as medicinals, from contamination with contaminants.
Further if the medicinal is contaminated with contaminants, decomposition of the medicinal, a change in its appearance, deterioration or like problem is likely to arise.
An object of the present invention is to provide a formability-improved medical multilayer sealant film having excellent heat-sealing properties and barrier properties to the foregoing contaminants.
Another object of the invention is to provide contamination preventing film for medical containers, medical container packaging film and medical container covering film which include the sealant film as the innermost layer.
Still another object of the invention is to provide contamination preventing products, such as a medical container, a medical container packaging bag (hereinafter referred to as a xe2x80x9cpackaging bagxe2x80x9d) and a medical container cover (hereinafter referred to as a xe2x80x9ccoverxe2x80x9d), which include the sealant film as the innermost layer.
Still another object of the invention is to provide a highly productive method of producing the above multilayer sealant film of high quality.
Other features of the present invention will be clarified by the following description.
The present invention provides a medical multilayer sealant film which is a multilayer sealant film having as the innermost layer a first layer comprising at least one resin selected from the group consisting of linear low-density polyethylene, low-density polyethylene, polypropylene and polybutene-1, the sealant film being characterized in that a third layer comprising an ethylene-vinyl alcohol copolymer is laminated to the outer side of the first layer with a second layer serving as an adhesive layer and comprising a resin containing, as a main component, at least one of an amorphous polyolefin, adherent polyolefin and ethylene-vinyl acetate copolymer, and in that the difference in density between the resin constituting the first layer and the resin constituting the second layer is 0.02 g/cm3 or less.
Still further, the present invention provides a method of producing a medical multilayer, wherein a co-extrusion inflation process is used to produce the above constructed multilayer sealant film, and wherein the lay flat width of the film is set to be 420 mm-1100 mm and the film take-off speed is set to be 7.0-15.0 m/min when forming the film.
The sealant film of the present invention may comprise, in addition to the three-layer structure of the first to third layers, a fourth layer and a fifth layer successively formed over the outer side of the third layer constituting the outermost layer of the structure.
In this case, the resin mentioned for the second layer is used for forming the fourth layer, and the resin mentioned for the first layer is used for forming the fifth layer, and the difference in density between both resins needs to be 0.02 g/cm3 or less.
The sealant film of the present invention is usable for forming the innermost layer of films for medical containers, medical container packaging films and medical container covering films.
The term xe2x80x9cfilms for medical containersxe2x80x9d as used herein refers to films for use in forming medical containers.
The term xe2x80x9cmedical container packaging filmsxe2x80x9d refers to films for forming packaging bags which wraps and seals off a medical container entirely (hereinafter referred to as xe2x80x9cpackaging filmsxe2x80x9d).
The term xe2x80x9cmedical container covering filmsxe2x80x9d refers to films for forming a cover which wraps in at least one compartment of a medical container locally adheres to the container (hereinafter referred to as xe2x80x9ccovering filmsxe2x80x9d).